1. Technical Field
The present invention relates to a fluid ejection device with a head cap that covers the nozzle surface of the fluid ejection head when the fluid ejection head is not operating, and relates more particularly to a moisturizing fluid supply control method that supplies water or other moisturizing liquid into the head cap to maintain a desirably wet state inside the head cap.
2. Related Art
Devices that use an inkjet head or other type of fluid ejection head that ejects fluid droplets from nozzles commonly cover and seal the nozzle surface of the head with a head cap when not printing to prevent ink left in the nozzles from drying and clogging the nozzles, and to prevent particulate from sticking to or getting in the nozzle surface or nozzles. Flushing, an operation that ejects ink droplets into the head cap from the nozzles of the inkjet head, is also regularly performed to prevent nozzle clogging. The ink droplets ejected in the flushing operation are collected in an ink absorbing member (sponge) inside the head cap, and the ink absorbed by the ink sponge is recovered by an ink recovery unit.
Waste ink absorbed by the ink sponge in the head cap gradually dries, ink viscosity increases, and dried ink accumulates. When the fluid ejection head is then capped, the high concentration of glycerine, diethylene glycol, or other humectant contained in the accumulated waste ink draws water from the ink in the nozzles of the inkjet head, thereby promoting increased viscosity in the ink inside the nozzles and inviting nozzle clogging and ink ejection problems. Water or other moisturizing fluid (referred to as simply water below) is therefore regularly supplied into the head cap to maintain a desirable level of wetness inside the head cap. Inkjet printers having this type of wetting function are described in Japanese Unexamined Patent Appl. Pubs. JP-A-2001-18408, JP-A-2001-253081, and JP-A-2008-105262.
Inkjet printers according to the related art with a function for keeping the inside of the head cap desirably wet have a dedicated water tank or water cartridge. In addition to replacing the ink cartridge that uses ink, this requires replacing the water (moisturizing fluid) as another consumable. The number of consumables that the user must therefore keep on hand increases, consumables must be replaced more frequently, and ease of use is decreased.
For example, the water supply timing varies according to how the user uses the inkjet printer (including printing time and interval between print jobs). As a result, during repeated high duty printing, ink consumption is high and water consumption is low, the ink cartridges must be replaced due to ink depletion more quickly than the water cartridge must be replaced, and the water cartridge must then be replaced sometime after the ink cartridge is replaced. Conversely, during repeated low duty printing, water consumption is high, and the water supply may be depleted before the ink cartridge needs replacing. In this case, the water cartridge must be replaced first. In both cases, however, cartridges need replacing more frequently because the ink cartridge and water cartridge are replaced at different times, thus increasing the user's workload. Not replacing the water cartridge when the water supply is depleted is also not desirable because the head cap cannot be kept desirably wet and problems such as clogged nozzles occur.